This invention pertains to an adjustable anti-roll bar, often called an anti-sway bar, used in conjunction with the suspension of xe2x80x9cstreetxe2x80x9d and racing cars.
Anti-roll bars are used in vehicles to adjust the torque of the suspension, whereby the roll rate can be influenced. Anti-roll bars are typically torsional springs which act across one axle to introduce resistance to relative changes in displacement of one wheel on that specific axle compared to the displacement of the other wheel on the same axle. The torsion spring is constrained both radially and axially and is connected to the suspension member in motion by a lever arm and a linkage. Taken together the lever arm and linkage is referred to in the art as a drop link.
The spring rate of an anti-roll bar may be fixed, that is non-adjustable and is determined by the dimensions of the anti-roll bar. Such anti-roll bars are known to the prior art. In addition, adjustable spring rates can be obtained by using a fixed dimension anti-roll apparatus having a plurality of aligned mounting hole pairs for attachment of the drop link. The chosen pair of mounting holes creates a change in length of the lever arm acting on the torsional spring. These also are known in the art. The change to the torsional spring rate of a vehicle having an anti-roll bar by any mode gives rise to what is termed a change to the roll stiffness of the vehicle.
Roll stiffness is important to both the ride comfort and the cornering ability of vehicles. Too little roll stiffness results in excess body lean and a slow response to changes of the steering wheel by the driver. On the other hand, too much roll stiffness creates a jittery uncomfortable ride which can cause a sudden loss of traction and the ability of the tires to stick to the road during cornering maneuvers.
The suspension and the anti-roll bar combination are predefined to give the vehicle certain riding characteristics. Thus, most vehicles are factory set to provide a roll stiffness balance to satisfy average usage, road conditions and driver preferences. This setting is commonly referred to as a xe2x80x9ctuned suspensionxe2x80x9d.
However, not all drivers are satisfied with the factory chosen specification. Indeed independent roll stiffness adjustments at the front and rear axles of a vehicle are often desired to balance the front and rear cornering adhesion limits for either safety or speed.
Many drivers desire to use a vehicle under conditions that deviate from the average daily driving conditions. Sometimes a driver may desire more vehicle feel and balance during driving. Contrast the handling of any given stock Chevrolet(copyright) with any given BMW(copyright).
Several instances of the desire to deviate from the norm can be mentioned. In the case of cars and trucks driven on smoother well maintained road surfaces or with tire and road interfaces having high adhesion, a maximum of roll stiffness would be desired. Vehicles driven in very wet climates, or on rough roads or dirty roads such as in under-developed countries are better suited to a softer stiffness for both comfort and driving security.
Race car drivers may desire a softer or a firmer suspension to achieve superior cornering of the vehicle. The nature of the track dictates the nature of the desired roll rate. Some of the influencing factors include the nature of the asphalt, wetness on the surface, dirt on the surface, and ambient temperature. If the track has low adhesion on a particular day, say, due to heavy rain, then to achieve maximum cornering the driver will desire a soft roll rate. But if the track has a high adhesion level, then a higher stiffness of the anti-roll bar is indicated in order to achieve maximum cornering capability of the vehicle.
Thus, the desire to be able to modify the roll rate of a vehicle can be readily understood. Heretofore, in order to make a change in roll stiffness, the driver either changed out the single hole mount sway bar, or used a flange adjustable sway bar or anti-roll bar. The prior art flange adjustable sway bars available in the marketplace use a bar of a specific configuration suitable to the car in question, with a mounting flange at each end, wherein the flange instead of having one mounting aperture has a series of usually up to three aligned apertures for mounting. The chosen mounting aperture dictates the nature of the roll rate as the torque is influenced directly by the flange aperture used in the mounting of the bar. It is believed that no one has previously devised an anti-roll, bar or sway bar that is adjustable across the middle of the bar as opposed to being adjustable at the mounting flanges.
According to the present invention, an anti-roll bar is provided wherein the active length of concentric central torsion springs can be readily varied. Such design capability is highly desired due to the fact that in many of today""s highly sophisticated automobiles, there is little or no room for the extra long flanges associated with the prior art adjustable drop link anti-roll bars to be able to change their position when and as the driver desires. Thus, the need for an apparatus having the features of the several embodiments of this invention can be readily seen.
Briefly, the invention comprehends an adjustable anti-roll bar comprising two elongated torsion members, one a hollow outer member, the other an inner member snugly received in the outer member, said members having a series of aligned diametrical openings at spaced intervals along their length, means at the end of said outer member for connection to one lever arm of a conventional vehicle suspension system and means at the end of said inner member for connecting to the other lever arm of a conventional vehicle suspension system, and fastening means inserted in any selected one of said series of diametrical openings to connect said inner and outer members whereby the stiffness of said anti-roll bar is determined.
It is a object therefore of this invention to provide an adjustable anti-roll bar that is adjusted by the proper placement of one or more fasteners.
It is a second object to provide two embodiments of this invention, both of which use the same concept for operation, but one of which utilizes a pair of opposed weldments to which the concentric members are attached in order to change the geometry to avoid interference with other car parts on the vehicle chassis.
Other objects of the invention will in part be apparent and will in part appear hereinafter.
The invention accordingly comprises the device possessing the features properties and the relation of components which are exemplified in the following detailed disclosure. For a fuller understanding of the nature and objects of the invention, reference should be made to the following description, taken in conjunction with the accompanying drawings.